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Warm and cold wet states in the Western United States during the Pliocene-Pleistocene

Daniel E. Ibarra, Jessica L. Oster, Matthew J. Winnick, Jeremy K. Caves Rugenstein, Michael P. Byrne and C. Page Chamberlain
Warm and cold wet states in the Western United States during the Pliocene-Pleistocene
Geology (Boulder) (April 2018) 46 (4): 355-358


The size distribution of lakes records the competition between precipitation delivery and evaporation. Lakes were abundant in the terminally draining basins of the western United States (USA) during both the colder-than-preindustrial latest Pleistocene glacial period (ca. 14-29 ka) and the warmer-than-preindustrial mid-Pliocene (ca. 2.9-3.3 Ma). To understand the hydroclimatic conditions that permitted lakes, we couple lake mass balance equations with a water and energy balance framework (sensu Budyko). Further, we compare paleo-lake area distributions to forward-modeled lake areas using climate model simulations of the Last Glacial Maximum (LGM, 19-26 ka) and mid-Pliocene. We conclude that both warmer- and colder-than-modern periods of the Pliocene-Pleistocene resulted in wetter-than-modern conditions in the terminally draining basins of the western USA through similar mechanisms. Specifically, the presence of lakes during the LGM reflects increased precipitation in addition to decreased evaporative demand. In the southern Great Basin, LGM lakes require large increases in precipitation across the region. During the mid-Pliocene, increased evaporative demand necessitated increased precipitation to maintain lakes. Further, the increase in precipitation and dominantly southwestern distribution of mid-Pliocene lake deposits is consistent with proposed mean "El Nino-like" conditions altering regional hydroclimate during this period. These observations suggest that during interglacial periods, the western USA resides within a local aridity maximum, and both long-term increases and decreases in global temperatures have been associated with wetter conditions across much of the western USA in the past.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 46
Serial Issue: 4
Title: Warm and cold wet states in the Western United States during the Pliocene-Pleistocene
Affiliation: Stanford University, Department of Earth System Science, Stanford, CA, United States
Pages: 355-358
Published: 201804
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2018-043946
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018106
Illustration Description: illus. incl. geol. sketch maps
Secondary Affiliation: Vanderbilt University, USA, United StatesEidgenoessische Technische Hochschule Zuerich, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2018
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